Cross-linking titanium &amp; zirconium chelates &amp; their use

ABSTRACT

Water-soluble N,N-bis-(2-hydroxyethyl)-glycine/metal chelates represented by the formula:   &lt;IMAGE&gt;   wherein R is H or alkyl (1-12C); M is Ti or Zr; k is a number in the range between 0 and 1, p is a number in the range between 1 and 2, and k+p=2 (in particular embodiments: k=1 and p=1; k=0 and p=2; and k=0.5 and p=1.5). The chelates can be used as cross-linking agents in hydraulic fracturing fluids and in gels that are used for selectively plugging permeable zones in subterranean formations or for plugging subterranean leaks.

CROSS-REFERENCE TO A RELATED APPLICATION

This is division of U.S. patent application Ser. No. 31,921 filed Mar.10, 1987 now U.S. Pat. No. 4,808,739.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to novel water-soluble titanium andzirconium chelates formed from N,N-bis-(2-hydroxyethyl)-glycine and atitanium or zirconium halide or ester. It relates also to the use of thechelates as cross-linking agents in hydraulic fracturing fluids, and ingels that are used for selectively plugging permeable zones insubterranean formations or for plugging subterranean leaks.

BACKGROUND OF THE INVENTION

Reactions of titanium or zirconium compounds with amino compounds areknown. For example, Yoshino et al., in the Bulletin of The ChemicalSociety of Japan, Vol.46, 2899 (1973), have reported their observationsin respect of certain mixtures of titanium and zirconium esters withnitrogen-containing compounds. Boiling a mixture of Zr isopropoxide andglycine dissolved in ethanol for 22 hours gave a white precipitate whichwas stated to be 2,5-piperazinedione. Substituting DL-alpha-alaline inthat mixture, gave a white precipitate which was said to be3,6-dimethyl-2,5-piperazinedione. When a mixture of glycine and Tiisopropoxide in isopropanol, and mixtures of glycine and Ti n-butoxidein ethanol and isopropanol, were heated to boiling, the glycine did notdissolve completely, but after 20 hours, light brown powders wereobtained which were stated to be 2,5-piperazinedione. Moreover, in U.S.Pat. No. 2,824,114, Bostwick disclosed compounds prepared by reacting analkyl titanium or zirconium ester with a monohydric, dihydric, ortrihydric monoamino or diamino alcohol, e.g., di-hydroxyethyl-ethylenediamine, and suggested using his compounds as dispersing agents and assurface active agents for hydrocarbons and waxes. Similarly Beacham etal., in U.S. Pat. No. 2,824,115, disclosed combining organo titanium andorgano zirconium compounds with polyhydroxyalkyl alkylene polyamines,and suggested using their compounds as dispersing agents, additives topaint and varnish formulations to improve durability, agents for thetreatment of wool and animal fibers, and in various textile and cosmeticapplications.

The use of zirconium compounds as cross-linking agents is described byKucera in U.K. patent application GB No. 2 108 122 A. Kucera disclosedreacting a zirconium alkoxide with a dialkanol amine or trialkanolamine, and suggested using the resulting compounds as cross-linkingagents in hydraulic fracturing of subterranean formations. Theproduction of oil and gas can be stimulated by the hydraulic fracturingtechnique, in which a fluid composition is introduced into an oil or gaswell at a flow rate and pressure which create and/or extend a fractureinto the oil- or gas-containing formation. The fluid composition usuallycarries a proppant (e.g., sand, bauxite, etc.) which is forced into thefracture by the fluid composition and prevents closure of the formationafter the fluid pressure is released. Tiner et al., in U.S. Pat. No.3,888,312, provide an example of the use of titanium-containingcross-linking agents in fluid or hydraulic fracturing. They disclosedhydraulic fracturing of subterranean formations using aqueous gelsprepared from a solvatable polysaccharide which had been cross-linkedwith ammonium tetralactotitanate(IV) orbis(triethanolamine)bis(isopropyl)titanium.

Recovery of oil from subterranean formations frequently involvesdisplacing crude oil with a driving fluid, e.g., gas, water, brine,steam, polymer solution, foam, or micellar solution. Ideally, suchtechniques (commonly called flooding techniques) would provide a bank ofoil of substantial depth being driven to a producing well; in practice,that frequently is not the case. Oil-bearing strata are usuallyheterogeneous, some parts of them being more permeable to a drivingfluid than others. As a consequence, channeling frequently occurs sothat the driving fluid flows preferentially through zones depleted ofoil (so-called "thief" zones) rather than through those parts of thestrata which contain sufficient oil to make oil-recovery operationsprofitable. High permeability zones can also cause undesirable loss ofdrilling fluids when a well (e.g., water, oil or waste disposal) isbeing drilled. Misplaced casing perforations or casing leaks are anothercause of channeling of the driving fluid through zones of highpermeability in the subterranean formations. In addition, casing leakssometimes occur in the annular region above the injection or productionpacker, and need to be dealt with whether the leaks occur in high or lowpermeability zones.

Hanlon et al., in U.S. Pat. No. 4,460,751, disclose a cross-linkingcomposition and the use of the compositions in a method for reducingpermeability of subterranean formations to water. They disclosepreparing the composition by mixing (1) water, (2) a Zr salt(oxychloride, acetate, tetrachloride, o-sulfate, carbonate), (3) an acidhaving the formula HO--C(═O)--CH(OH)--R wherein R is H or alkyl (1-3 C)and (4) a amine having the formula R¹ N(R²)R³ wherein R¹ is hydroxyalkyl(1-3C), R² is alkyl (1-3 C) or R¹, and R³ is H or R².

The products of the present invention provide advantages over those ofthe prior art. For example, the titanium- and zirconium-containingcompositions of the present invention have extremely slow rates ofcross-linking. They can therefore be used at high temperatures and/or athigh pH and still effect crosslinking at acceptable rates. Thus, forexample, they can be used in a well completion fluid which contains ahigh level of brine. Consequently, the compositions of the presentinvention can be used in hotter geologic formations, including those atgreater depths in oil and gas wells. In addition, the compositions ofthe present invention are better suited as cross-linkers than are thoseof the prior art in cross-linked gels used in hydraulic fracturingfluids and for plugging leaks and selectively plugging permeable zones.

DETAILED DESCRIPTION OF THE INVENTION

The water-soluble N,N-bis(2-hydroxyethyl)-glycine/metal chelate of thepresent invention can be represented by the formula: ##STR2## wherein Ris H or alkyl (1-12C); M is Ti or Zr; k is a number in the range between0 and 1, p is a number in the range between 1 and 2, and k+p=2 (inparticular embodiments: k=1 and p=1; k=0 and p=2; and k=0.5 and p=1.5).

The water-soluble N,N-bis(2-hydroxyethylglycine/metal chelates can beprepared by reacting a titanium or zirconium halide or alkoxide withbetween one and two molar equivalents ofN,N-bis-(2-hydroxyethyl)-glycine. Various titanium and zirconium halidesand esters can be used for the purposes of the present invention, e.g.,Ti(OR)₄ or Zr(OR)₄ wherein R is alkyl containing 1-12 carbons, TiCl₄,ZrCl₄, TiOCl₂ or ZrOCl₂, with ZrOCl₂ being preferred. ZrOCl₂ may be usedas such or it can be formed in situ by reacting ZrCl₄ with H₂ O.N,N-bis(2-hydroxyethyl)-glycine may be present as an amine salt when aTi or Zr ester is used. The reaction of the titanium and zirconiumhalides and esters with the glycine derivative can be carried out at avariety of temperatures, e.g., between 15 and 100 degrees C., preferablybetween 20 and 60 degrees C.

In the hydraulic fracturing process of this invention, one or morefractures is created or extended in an oil- or gas-containingsubterranean formation by introducing a cross-linked gel formed from asolvatable polysaccharide into the formation at a flow rate and pressuresufficient to create or extend such a fracture. Another embodiment ofthe present invention relates to a process for selectively pluggingpermeable zones in subterranean formations or for plugging subterraneanleaks which comprises injecting into the permeable zone or the site ofthe subterranean leak a cross-linked gel formed from a solvatablepolysaccharide. The cross-linking agent for each process is one of thezirconate/N,N-bis-(2-hydroxyethyl)-glycine chelates of this invention.

The solvatable polysaccharides include guar gum and locust bean gum, aswell as other galactomannan and glucomannan gums, such as those derivedfrom sennas, Brazilwood, Tera, Honey locust, Karaya gum and the like.Derivatives of gums are useful also, e.g., hydroxyethylguar,hydroxypropylguar, carboxyethylhydroxyethylguar,carboxymethylhydroxypropylguar, and the like, as well as cellulosederivatives containing carboxyl groups, such as carboxymethylcellulose,carboxymethylhydroxyethylcellulose, and the like. Hydroxypropylguar andcarboxymethylhydroxypropylguar are preferred polysaccharides for use inthe present invention. Hydroxypropylguar is the most preferred gum basedupon its commercial availability and desirable properties. On the otherhand, carboxymethylhydroxypropylguar is sometimes used in place ofhydroxypropylguar in fracturing fluids when the permeability of theformation is such that one wishes to keep the residual solids at a lowlevel, so as to prevent formation damage. The solvatable polysaccharidescan be used individually or in combination; usually, however, a singlematerial is used. The solvatable polysaccharides are normally blendedwith a solvent such as water or an aqueous medium (e.g., aqueousmethanol, ethanol, 1 to 3% HCl or potassium chloride) to form anuncross-linked gel as a first step.

The amounts of solvatable polysaccharide and the cross-linker thereforvary. One uses small but effective amounts which for both will vary withthe circumstances, e.g., the type of geologic formation, the depth atwhich the process (e.g., fluid fracturing, permeable zone plugging orleak plugging) is to be performed, temperature, pH, etc. In all cases,one uses as small an amount of each in water as will provide theviscosity level necessary to effect the desired result, i.e., fracturingof the subterranean formation, or plugging leaks or permeable zones tothe extent necessary to promote adequate recovery of oil or gas from it.For example, satisfactory gels can generally be made for fluidfracturing by using the solvatable polysaccharide in amounts up to about1.2 weight percent and up to about 0.30 weight percent of thecross-linker, both percentages being based on the weight of the aqueousliquid. Preferably, from about 0.4 to about 0.75 weight percent of thesolvatable polysaccharide is used and from about 0.05 to about 0.10weight percent of the cross-linker. For plugging leaks or permeablegeologic zones, one generally uses about 0.40 to 1.2 weight percent of asolvatable polysaccharide, preferably 0.40 to 0.75 weight percent, and0.04 to 0.30 weight percent of the zirconium chelate, preferably 0.05 to0.10 weight percent.

The following Examples are given in further illustration of theinvention but not by way of limitation. Preparation of the compositionsin the Examples were carried out in a closed vessel containing anagitator, thermometer, condenser, nitrogen inlet and dropping funnel.Unless specified otherwise, percentages are given by weight.

EXAMPLE 1 (Best Mode)

N,N-bis-(2-hydroxyethyl)-glycine (53.6 mols; 8748.6 g) was added withstirring to aqueous zirconium oxydichloride (53.6 mols; 32,986.8 g of anaqueous solution having a Zr content of 14.8 wt. %) over a period ofabout 2 hours and 15 minutes, causing the temperature to drop from 23 to18 degrees C. and giving a clear yellow liquid. The mixture was stirredfor about 1 hour more, during which time the pot temperature rose to 20degrees C. The clear yellow liquid had a pH of about 0.5. Aqueous sodiumhydroxide (14128 g of a 30 wt % solution) was added over a period of 4hours and 10 minutes to a pH of 7.3 and a pot temperature of 42 degreesC. The reaction mixture was heated to 60 degrees C. and held at thattemperature for about 2 hours and 20 minutes. Yield=55,367 g of a hazyliquid product containing about 8.83 wt. % Zr and having a density of1.282 g/ml.

The cross-linking properties of the chelate are given below as afunction of the viscosity of hydroxypropylguar cross-linked with thezirconate/bis-(2-hydroxyethyl)-glycine chelate of EXAMPLE 1. For a pH9.9 gel, one blends for 30 minutes in a Waring Blender at a pH of 3.1: afumaric acid buffer, 4.5 g of hydroxypropylguar and 0.9 g of sodiumthiosulfate in 750 ml of 2% by weight KCl. To that gel in a 1500 mlbeaker one adds 0.75 ml of cross-linker solution containing 0.00064 molof zirconium, and mixes vigorously for about 15 seconds to about 3minutes. A 25 ml sample of that cross-linker containing gel is placed inthe cup of the FANN 50 Viscometer with an R-1, B-3 configuration at 250degrees F. (121 decrees C.) and 100 rpm (88 sec⁻¹) shear.

When tested using the foregoing procedure, the chelate of Example 1 gavea crosslinking rate of 11.5 minutes and the viscosities set forth inTable 1.

                  TABLE l                                                         ______________________________________                                        Time (min)    Viscosity (cps)                                                 ______________________________________                                         0            132                                                              5             90                                                             10            435                                                             20            402                                                             30            390                                                             40            378                                                             60            369                                                             90            359                                                             ______________________________________                                    

EXAMPLE 2

N,N-bis-(2-hydroxyethyl)-glycine (1.28 mols; 208.3 g) was added withstirring to aqueous zirconium oxydichloride (1.28 mols; 785.4 g of a 29wt. % solution) over a period of about 30 minutes, causing thetemperature to drop from 23 to 16 degrees C. The mixture was stirred atabout 23 degrees for 30 minutes more, during which time the temperatureof the mixture rose to 23 degrees C. The resulting clear yellow liquidhad a pH of about 0.5. Aqueous sodium hydroxide (387 g of a 30 wt %solution) was added over a period of 30 minutes to a pH of 7.4, whilemaintaining the pot temperature at about 20 degrees C. by use of an icebath. The reaction mixture was heated to 60 degrees C. and held at thattemperature for about 2 hours. Yield=1365.6 g of a water clear productcontaining about 8.85 wt. % Zr and having a density of 1.281 g/ml.

EXAMPLE 3

The procedure of EXAMPLE 2 was repeated at aN,N-bis-(2-hydroxyethyl)-glycine/zirconium oxydichloride molar ratio of2/1, resulting in a liquid product having a Zr content of 7.31 wt. % anda density of 1.282 g/ml.

EXAMPLE 4

Methanol (250 ml) was added with stirring toN,N-bis(2-hydroxyethyl)-glycine (0.254 mol; 40.8 g) to give achalky-white suspension. Over a period of one hour, zirconiumtetra-n-propoxide (0.125 mol; 56.5 g of a solution in n-propanolcontaining 21.5 wt. % Zr) was added with stirring at 50 degrees C.Stirring was continued for two additional hours at 50 degrees. Heatingand stirring were discontinued and the reaction mixture was allowed tostand overnight, giving a yellow liquid product, the upper two/thirds ofwhich was clear, and the lower one/third of which contained whitesolids. The reaction mixture was heated to reflux and additionalmethanol (150 ml) was added. After two more hours at reflux, a clearyellow liquid product (360.7 g), containing 3.2 wt. % Zr and having adensity of 0.866 g/ml, was obtained.

EXAMPLE 5

The procedure of EXAMPLE 4 was repeated at aN,N-bis-(2-hydroxyethyl)-glycine/zirconium n-propoxide mol ratio of 1/1to give a slightly hazy yellow liquid product containing 5.4 wt. % Zrand having a density of 0.88 g/ml.

EXAMPLE 6

N,N-bis-(2-hydroxyethyl)-glycine (0.15 mol; 24.2 g) was added withstirring at about 20 degrees C. to a mixture of triethyl amine (0.21mol; 21.2 g) and methanol (40 ml). After heating to reflux (about 60degrees C.) and adding 16 ml of water, the resulting amine salt of theglycine derivative went into solution. The solution was cooled to 40degrees C., and tetrakis-(isopropoxy)-Ti (0.1 mol; 28.4 g) was addeddropwise with stirring. After stirring an additional hour at 40 degreesC, the clear liquid product (107.9 g) was bottled. Upon standingovernight, some solids separated from the liquid product. Addition of4.2 g of water gave a clear solution (112.1 g) containing 4.3 wt % Tiand having a density of 1.017 g/ml.

EXAMPLE 7

The procedure of EXAMPLE 6 was repeated at aN,N-bis-(2-hydroxyethyl)-glycine/tetrakis-(isopropoxy)-Ti molar ratio of2/1, giving a clear solution having a Ti content of 3.1 wt. % and adensity of 0.99 g/ml.

What is claimed is:
 1. In a process for selectively plugging permeablezones in subterranean formations or subterranean leaks wherein across-linked gel formed from a water solvatable polysaccharide isinjected into the permeable zone or the site of the subterranean leak,the improvement comprising effecting crosslinking of the gel with awater-soluble N,N-bis(2-hydroxyethyl)glycine/metal chelate representedby the formula: ##STR3## wherein R is H or alkyl (1-2 C); M is Ti or Zr;k is a number in the range between 0 and 1, p is a number in the rangebetween 1 and 2, and k+p=2.
 2. The process of claim 1 wherein M is Zr.3. The process of claim 2 wherein each of k and p is
 1. 4. The processof claim 2 wherein k is 0 and p is
 2. 5. The process of claim 1 whereinM is Ti.
 6. The process of claim 5 wherein k is 0.5 and p is 1.5.
 7. Theprocess of claim 5 wherein k is 0 and p is
 2. 8. In a hydraulicfracturing process wherein a cross-linked gel formed from a watersolvatable polysaccharide is introduced into a subterranean oil- orgas-containing formation at a flow rate and pressure sufficient tocreate or extend one or more fractures therein, the improvementcomprising effecting cross-linking of the gel with a water-solubleN,N-bis(2-hydroxyethyl)glycine/metal chelate represented by the formula:##STR4## wherein R is H or alkyl (1-l2C); M is Ti or Zr; k is a numberin the range between 0 and 1, p is a number in the range between 1 and2, and k+p=2.
 9. The process of claim 8 wherein M is Zr.
 10. The processof claim 9 wherein each of k and p is
 1. 11. The process of claim 9wherein k is 0 and p is
 2. 12. The process of claim 8 wherein M is Ti.13. The process of claim 12 wherein k is 0.5 and p is 1.5.
 14. Theprocess of claim 12 wherein k is 0 and p is 2.